Lithography refers to a process which is used to manufacture semiconductor integrated circuit elements. A lithography process includes coating a semiconductor wafer so as to have a photosensitive layer and exposing the photosensitive layer by transmitting an actinic light source onto a photomask having an image of an integrated circuit.
The photomask which is used for the lithography process includes various mask patterns. In certain instances, individual mask patterns which are included in the photomask are configured, for example, by combination of various variables such as a shape, a line width, and an interval between patterns.
In the lithography process which forms a semiconductor integrated circuit element on a semiconductor substrate, even though a transferred pattern is formed on the photosensitive layer using an optical focus of an exposure apparatus, a focus shift may occur in one or more mask patterns which are included in the photomask.